(a) Field of the Invention
The present invention is concerned with a flashing device attachable to a motion picture camera for subjecting the film just before or after its principal exposure through the camera's lens aperture to a supplementary uniform exposure in order to achieve a visual effect such as, for example, a fogging effect, a color mood effect or an enhancement of latent images.
(b) Brief Description of the Prior Art
Flashing is a well-known photographic technique which basically consists in subjecting a negative film to a low-intensity exposure that is uniform and non-image-forming prior to development, in order to achieve some visual effect such as:
a fogging effect, due to a reduction of the contrast (neutral flashing);
a color mood effect, due to an alteration of the normal color rendition of the developed negative (non neutral flashing);
to obtain a higher effective emulsion speed in connection with force development without altering the photographic quality;
the reduction of the fill light used when recording scene; and
the matching of films that were differently exposed.
In practice, flashing can be carried out before, during or after normal exposure of the films, that is during its fabrication (see, for example, U.S. Pat. No. 3,819,376), during its exposure to an image-forming light in a camera (see for example, U.S. Pat. Nos. 3,577,898; 3,528,737; 3,823,413; 3,827,071; 3,936,852 and 4,172,640) or during its development (see U.S. Pat. No. 3,455,633).
It is technically recognized in the literature that there is no substantial difference in effect if flashing is carried out before, during or after normal exposure of the film although flashing carried out during normal exposure has some advantages as compared to the pre-and post-exposure, such as:
to allow variation of the flashing effect during exposure of a scene;
to allow compensation of variation in colour transmissability between two lenses when different lenses are used for filming a scene;
to allow correlation of any supplementary speed-enhancing light in accordance with the scene light; and/or
to check immediately the effect of these variation, compensation and/or correlation when use is made of special devices as disclosed in U.S. Pat. Nos. 3,827,071 and 3,936,852, which devices are attachable to the front of the objective lens of a camera for directing additional light directly to this lens to supplement the light reaching the film from the scene being recorded.
In addition to allow immediate verification of the flashing effect through the objective lens of the camera, the special devices disclosed in U.S. Pat. Nos. 3,827,071 and 3,936,852 have the substantial advantage of being usable with any kind of cameras without having to alter the structure of the objective lenses, as is called for in U.S. Pat. Nos. 3,577,898 and 3,528,737.
In spite of these advantages, these special devices are not used as much as they should in the motion picture industry because of their costs which are rather high, of their weights which are substantial, and of the difficulties they bring out when one wants to exchange one lens for another.
As an alternative to these devices, U.S. Pat. No. 4,172,640 issued on Oct. 30, 1979 to POLAROID CORP. discloses a cassette holding motion picture camera comprising a built-in supplemental exposure system. The supplementary exposure light generated by a small lamp housed in a lateral chamber is directed to the side of the film which is opposite to the side exposed to the image forming light passing through the objective lens, by means of an optical prism incorporated into the film cassette. An electronic circuit is provided to adjust the flashing intensity and duration of the supplementary light which is switched on in synchronization with the opening of the objective shutter. A filter disc insert is also provided to allow insertion of filters of different intensities in such a position as to vary and control the wavelengths of the light directed to the film.
The flashing system disclosed in this U.S. Pat. No. 4,172,640 has numerous advantages including, inter alia, the fact that it is light and it allows the operator to change the objective lenses of the camera in a very easy manner whenever desired. This flashing system however is of the built-in type, thereby restricting its use to a given type of camera and cassette.